The present invention pertains to a device for backing book blocks.
EP 0 676 303 B1 shows a device for backing book blocks (FIGS. 11 and 12), in which the supporting bearing is laterally supported against the effect of disc spring assemblies in the form of a spring element such that a pressing force for turning over the sheets of the book block is applied in the lateral regions of the spine. During the return stroke of the pressing beam toward the center of the block spine, the effect of the disc spring assembly is neutralized in order to prevent the outer sheets that are laterally turned over from being carried along. In this case, the motion of the pressing beam may be additionally controlled such that it clears the block spine during its return stroke due to an upward motion and is subsequently placed back on the spine in the block center in order to back the opposite side of the block spine.
The control of the disc spring assemblies and therefore the lateral position of the supporting bearing is realized with rams that are arranged laterally of the supporting bearing and controlled by cam wheels, wherein these rams act upon the supporting bearing in alternating directions and transfer the disc spring assemblies from a supporting position for applying a pressing force into a relieving position.
The above-described position control, in which the spring force is relieved, makes it possible to back sheets with high as well as low rigidity without causing the sheets to buckle or to be pushed back again. In this case, it suffices to back each side of the block spine once in order to achieve the desired mushroom-like spine shape.
When the pressing beam is centrally placed on the block spine, it may occur, however, that the pressing beam causes the central sheets to buckle such that creases are formed. A loose contact between the pressing beam and the center of the block spine, in contrast, reduces the smoothing of the elongations in the glue film caused by the rounding, whereby the previously created rounding in the center of the block spine is stabilized.